The movie starts with a police chase. Cops are chasing after a kid, Sean Anderson, on a motorcycle at night which goes through a fence and up a swing set before landing in a swimming pool. The cops approach him, and as he sits in the back of the ambulance, Hank (Dwayne Johnson) shows up. He’s the kid (Sean’s) “stepfather” or legal guardian, and he takes him home.
When they get home Sean’s mother Liz (Kristin Davis) yells at him. He had broken into a satellite facility. He’s very angry as he was forced to move due to his mother’s marriage to Hank. He goes into his bedroom which is covered in pictures and magazine articles.
The next day Hank knocks on Sean’s door to try and talk to him. Hank is smiling and tries to connect with Sean over the things he’s looking at such as papers with Morse code. It turns out Sean was trying to access a signal broadcast inside the satellite facility with words he is trying to decode. Hank tells Sean they’ll solve it together - but Hank knows how to decode it from the Navy. The message reads “The island is real.” Sean flips out in excitement as he decodes the rest of the message. “Stevenson” (as in Robert Louis Stevenson) is part of it which leads them to Treasure Island. The word Swift leads them to Gulliver’s Travels. The other book they have is Jules Verne’s Mysterious Island. Sean has the idea that no one has ever found Mysterious Island because they never used all three books to find it, when they all could be about the same island. Hank rips a page from each book that has a map of the island on it. Put together with a light one map is shown with the coordinates.
Sean immediately starts packing to go to the island, and Hank reminds him that he’s a teenager. Sean says that the person behind the message is his grandfather, and he has to go. Sean tells Hank that he needs to just worry about his mother and leave him alone. The next morning Hank is talking to Liz about what happened. Liz says that the grandfather (Alexander Anderson) is not who Sean thinks he is, but was a deadbeat dad instead. Hank wants to bond with Sean and he tells him the good news They’re going to Palau! Sean is less than enthused that Hank is going with him.
Before long they’re in Palau and Sean is speaking broken English to the natives, not realizing that they speak English. The ship captain refuses to take them, even for $1,000, but another captain, Gabato (Guzman), willingly takes them on his helicopter. We then see his teenage daughter Kailani (Hudgens), who of course Sean is in love with. Kailani tells them that where they want to go is deadly and they’ll take them for $3,000.
Gabato makes a lot of jokes and Sean fails at his attempts to flirt with Kailani. Just then there’s a huge storm/hurricane making the helicopter shake. Sean tells them that they have to fly into the eye of the hurricane to get to the island, but they think he’s crazy. Gabato tries to get out but his controls are broken. They fly into the eye of the hurricane, everything is flying everywhere, and just as they hit the water it goes black. Sean wakes up on the island telling Hank he has to believe, since everyone is stunned. They’re on the island, which is not what Sean pictured. He thinks he found a way off the beach and they travel through a cave, while hearing weird sounds. As they leave the cave, they see the “mysterious island.” It’s beautiful and the animals are all different sizes. Big animals are now small, and small animals are now large, like in Gulliver’s Travels (they pick up a tiny elephant). They see smoke and Sean starts to go but Kailani and Gabato want to go back to the beach. Hank convinces them to stick together until they find the grandfather and are able to call for help.
As they’re walking they think they’re stepping on giant rocks, but they realize they are eggs. Then they spot a giant lizard and try to walk carefully, but Gabato cracks and falls INTO an egg. The lizard starts to chase them after he gets out but they manage to escape (even though at one point Sean flies through the air and you think he’s going to get eaten) thanks to Alexander (the grandfather, played by Michael Caine). He meets them and takes them back to his house in a tree which has an elevator and plumbing. He tells them that it took 3 years to create the radio signal and they can’t get help for two weeks. Sean is happy, but everyone else is upset, and Hank and Alexander continuously insult each other.
The next day they’re traveling through the island and Sean once again fails at flirting with Kailani. Hank stops him and gives him advice, such as do the opposite of your instincts, be in touch with his emotions, and pop your pecs. He has Sean toss berries at his pecs and they all just bounce off. Finally, they find where they were going The Lost City of Atlantis.
While everyone is busy being excited about the discovery, Hank discovers that the island will be sinking in 2-3 days, not in years like Alexander thought. Sean remembers the Nautilus Captain Nemo’s submarine they could use it to ride under the hurricane back to Palau. Of course, now they must find Captain Nemo.
They go to Captain Nemo’s tomb and Kailani enters it alone to look for the journal which has the submarine’s location written in it. When she grabs it the entire tomb starts to cave in very Indiana Jones-esq; however she escapes in time. After reading the journal, Alexander tries to think of the best way to get to the location. He tells them that it’s very dangerous, and they all seem up for the adventure.
During their journey they see a volcano that has gold, and while Sean wants to stop, Hank tells them that they have to keep going or they will run out of time, so they keep going. Kailani and Sean finally start talking about how annoying their “dads” can be, and Kailani makes Sean realize that it’s good that Hank cares so much. They finally get close to where they need to be, but they’re at the bottom of the cliff and need to get to the top. Alexander hops onto a giant bee to fly to the top. They all mount their own bees and fly to the top of the cliff. They all start laughing when a bird poops on Gabato’s head, until they see it and it starts chasing after them since it eats bees. Suddenly there’s two birds chasing them through the trees.
During the chase, Kailani falls off the bee, however Sean manages to catch her on the bee before she hits the ground, but the bird is still after them. He lets Kailani down, and everyone else is down as well, as he gets the bird to follow him until it gets stuck in a spider web. Right after Sean falls off the bee and injures his ankle. They set up camp for the night and pop his ankle back into place (ouch!). Hank, Sean, and Alexander have a pleasant evening by the campfire singing and talking. It’s revealed that Hank’s father left when he was eight years old.
Gabato and Kailani are off by themselves talking about finances. Gabato promises her that if she wants to go to college she can. The next morning, they all wake up in water, meaning that the island is sinking fast. Forget a couple of days, more like hours. They also discover that Gabato has left to go back to the volcano of gold so they can afford a decent life. Since Sean’s ankle is preventing him from going with Kailani to find him, Alexander volunteers. He gives Hank and Sean directions on what to do. Sean and Kailani hold hands and say goodbye.
Hank and Sean reach Poseidon’s trident which is where the Nautilus is supposed to be but it’s not. They realize that it’s hidden because of the rising sea level. They construct a breathing device to be able to reach it. They jump into the water and find the submarine. They attempt to open the hatch and finally do despite a giant electric eel that gets in their way. Inside the Nautilus, they discover that the engine is dead. To jumpstart it, they realize they need the electric eel’s help. They get everything set up and Sean is afraid that something will happen to Hank. He tells him that he NEEDS him to come back. They have a bonding moment where Hank tells him that he’s his son now and he will come back for him. Hank is outside with a diving suit he constructed, trying to lure the eel. He throws a harpoon at the eel and the power goes on.
Meanwhile, we see Gabato has stumbled across gold. Kailani and Alexander find him and convince him that they don’t need gold to be rich. They all start to go back to find the submarine but they get lost as the compass isn’t working properly. They figure out which way is north by using spiderwebs which face the south…of course they also see a giant spider just as it’s starting to storm and a volcano is erupting. They’re holding on by floating on a piece of land/rock that broke off. They jump into the water and Gabato sees the submarine. They all manage to get inside and dodge a lot of rocks to escape thanks to Gabato steering the ship and firing rockets at the rocks/falling land. Once safe, Hank tells Sean to “pop his pecs” for Kailani and they kiss.
Six months later, Gabato has a successful tourism business in Palau and was able to send Kailani to college in America. Kailani is dating Sean. On Sean’s birthday they are all celebrating as a family. He receives the book From the Earth to the Moon from Alexander, who shows up on a motorcycle as a surprise. He suggests they go on another adventure to the moon all together and Sean asks, “Who’s up for an adventure?”
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